textproduct: Rapid City
This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.
KEY MESSAGES
- Cool temperatures for the remainder of the weekend
- Rainfall chances overnight looking a little less likely, with better chances coming Sunday night
- Seasonal temperatures through the week, with rainfall chances returning by midweek.
DISCUSSION
(This Evening Through Saturday) Issued at 1237 PM MDT Sat Sep 12 2026
Latest water vapor imagery shows broad upper high pressure located across the southern tier of the country with a digging 500hpa low off of the Pacific NW coast. Quick moving zonal flow is found across the upper midwest. At the surface high pressure is located across much of the western Dakotas with a weak surface trough sliding southeast across eastern SD. At 18Z skies were mainly clear to partly cloudy except for along the ND/SD border where more clouds were found. Temperatures were in the mid 50s to mid 60s.
Models are still advertising 700hpa theta-e ridge and associated forcing to slide across southern tier counties overnight. Did trim back inherited pops but am still a bit concerned that we might be overdoing the forecast. Ensembles are only showing 10-20 percent probabilities of seeing greater than 0.01 inch of rain across our southern counties, and less than that of seeing 0.05 inch of rainfall.
Sunday will looks to be dry to begin with and becoming breezy with easterly upslope flow. This will result in a few more clouds which will aid in keeping temperatures down a bit more. Sunday night into Monday morning main upper trough finally kicks out across region with associated 700hpa theta-e ridge and forcing. Better moisture tracks along with this feature and this is when our best chance of seeing rainfall occurs. As the moisture shield tracks west to east it will become more widespread. Expecting more to fall is rain, although can't rule out some scattered thundershowers here or there through the period.
The remainder of the week looks to be seasonable temperature wise, with rainfall chances returning back to the forecast area around mid-week.
AVIATION
(For the 18Z TAFS Through 18Z Sunday) Issued At 1245 PM MDT Sat Sep 12 2026
VFR conditions are expected through the TAF period. Gusty conditions are also expected Sunday afternoon.
UNR WATCHES/WARNINGS/ADVISORIES
SD...None. WY...None.
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